Pictured here is what the McLeod looks like up against the weighted early 89 flywheel. You can really see the difference.

The stock flywheels weights around 30 to 40 pounds, while the McLeod flywheel, a light weight aluminum setup with a steel insert for the contact area, weights only 14 pounds.

The principal of a lighter flywheel is easy to understand. It takes less force to make a light object, say a basketball, than it would a heavier object, say a cannon ball. The principal is the same with the flywheel, it takes less force to rotate the flywheel and therefor you actually acquire more force at the rear wheels. If your drag racing your flywheel's rotational velocity will change at least 8 times in the course of the track (assuming you use four gears). When you accelerate the flywheel speeds up and then each time you shift the flywheel slows down, so for each time you shift gears, you are changing the rotational velocity twice. The less weight you have to turn, the quicker the engine can spin up and the more you can get to the rear wheels.